Electrodynamic device



Feb. 20, 1934. B. A. ENGHOLM 1,948,207

ELECTRODYNAMIC DEVICE Filed June 16, 1952 Patented Feb. 20, 1934 UNITED STATES,

ELECTRODYNAMIC DEVICE Bernard A. Engholm, Lakewood, Ohio, assignor to The Bola Company, Cleveland, Ohio, a corporation of Ohio Application June 16, 1932. Serial No. 617,525

7 Claims.

This invention relates to electro-dynamic devices of the type wherein a moving voice coil is connected to a diaphragm. Heretofore, considerable difficulty has been experienced in properly supporting the coil and diaphragm, so as to permit the occurrence of the proper piston action and yet maintain proper axial alignment between the moving coil and the pole pieces of the stationary coil. Furthermore, considerable objection has been found to exist in the construction, particularly from the viewpoint of servicing a device in the replacement of the diaphragm.

One method of flexibly supporting the inner end of a conical diaphragm has been to utilize a flexible spider which surrounds the neck of the diaphragm and the associated moving coil form, and which is attached to the outer end thereof by threaded securing members to the housing or field coil assembly. This construc tion also included the assembly of the diaphragm housing, front plate, coil shell and field core assembly with the subsequent assembly of the diaphragm moving coil and spider, and fastening by means of screws and nuts of all of the parts into a complete unit. This makes a very tedious operation, for it is difficult to apply any wrenches or other tightening means into a housing after the parts are assembled. Furthermore, the use of such fastening means for the spider has a tendency to distort and twist it, thus misaligning the voice coil with reference to the inner and outer pole pieces when the spacing templet is removed. A further criticism of previous types of assembly is the difliculty, which has been experienced in maintaining proper axial relationship between the moving coil and the inner and outer pole pieces. For example, in centering the unit, the practice has been to center the coil with reference to the outer pole piece and then to center the inner pole piece to the core. This necessitated the use of an adjustable inner pole piece tip, but final adjustment of the inner pole piece is apt to be incorrect with reference to the outer pole piece, for any'error in its adjustments is progressive in its nature.

An object of the present invention therefore, is to eliminate the objections heretofore noted to provide a unit, which may be assembled more expeditiously, and to permit the replacement of the diaphragm and moving coil without disturbing the alignment of the pole pieces, and without dismantling the field coil and diaphragm housing.

In this connection, my invention contemplates a. construction, wherein the diaphragm and spider assembly may be accurately and quickly aligned with reference to the inner and outer pole pieces of the field coil, and then clamped without placing any torsional stresses on the spider and its associated diaphragm and coil form. Furthermore, my invention is directed toward a construction wherein the clamping operation may be effected by the application of threaded members to parts which are easily accessible from a point outside the unit. This has important manufacturing features as well as servicing advantages in the. replacement of the diaphragm and its associated parts.

Referring now to the drawing, Fig. 1 is a side elevation partly in cross section of an ,electrodynamic device embodying my invention; Fig. 2 is a section on the line 2--2 in Fig. 1; Fig.3 is a perspective view of the spider which is intended for holding the diaphragm and moving coil assembly in proper position; Fig. 4 is a perspective view of a clamping arm that is used for holding the spider in adjusted position, and Fig. 5 is an enlarged section adjacent the connection between the spider and the diaphragm.

An electrodynamic device with which I have shown my invention comprises a loud speaker having a fieldcoil 10, a shell 11, an inner pole piece 12, an outer pole piece 13, a diaphragm 14, a moving core 15, a diaphragm supporting housing 16, a clamping ring 17 and a spider18. The spider embodies a flexible member'which may have a central opening 19 that embraces the neck 20 of the diaphragm and that is fastened thereto by cement. The neck of the diaphragm in turn is shown as embracing the forward end of the moving coil form 21.

The present invention is especially concerned with the manner of supporting the spider with reference to the field coil and housing assembly. To this end, the spider is shown as being held by adjustable clamping members, or bridge pieces which permit movement of the spider universally until proper adjustment between the moving coil and the pole structure is obtained, and which enable the spider to be clamped in such adjusted position by tightening fastening members which are accessible from a point outside the unit.

The preferred form of clamping device includes arms 25 which are provided with threaded openings 26 intermediate the ends thereof for receiving screws 27, the heads of which are disposed outside the back flange 28 of the housing 16. Reference to Fig. 2 shows that the screws are disposed outside the lines 29 which define the top and bottom edges of the flanges on the coil shell 11. Each of the arms are adapted to hear at one end against the inner side of the housing, and accordingly each arm may be bent toward the flange 28 and provided with a tongue 30 which passes through an opening 31 in the housing flange. The end portions of the arm on each sideof the tongue thus provide shoulders against which pressure may be exerted when the screws 27 are tightened to draw opposite ends of the arms into frictional engagement with the spider. In practice, the screws are loosened until the moving coil and the spider and diaphragm as a unit, are axially aligned with reference to tionary support,

means, said last mentioned means including a bridge piece that engages the spider and support, and extends across an outer edge thereof.

2. In an electro-dynamic device, the combination with a diaphragm, a moving coil and a flexible supporting spider, of a stationary support, arm's frictionally engaging the spider and means for locking the arms to the support.

.3- In an electro-dynamic device, the combination with a diaphragm, a moving coil and a flexible spider, all interconnected as a unit, of a staclamping members bearing against the support and also against the spider, and means for locking the clamping members against movement with reference to the support.

If desired, the spider may be provided with tabs 35, which are adapted to be positioned beneath the clamping arms. However, to facilitate the registration of the tabs with the clamping arms, I may provide slots 36 in the tabs and a tongue 37 on each arm that is adapted to enter one of the slots. The tongue is shown in Fig. 1 as ex,- tending through an opening in the flange 28, and thus as being locked against any tendency to twist when the screws 27 are tightened.

From the foregoing description, it is apparent 1 that the field coil and housing assembly may be manner.

connected as a unit by the use of securing members 40, which have heads that are accessible from a point outside the device. At such time, the front plate or outer pole piece 13, may be axially adjusted with reference to the core or inner pole piece 12. In the meantime, the diaphragm moving coil and spider assembly may be fabricated as a unit, and then inserted into the housing and centered by templets in the usual The outer end of the diaphragm is then fastened into place, by riveting or otherwise fastening it between the clamping ring and the outer flange of the housing, and then the spider is clamped. It is therefore, apparent that this method of assembly enables the moving coil assemblyto be axially aligned, and then clamped without placing any torsional stresses on the spider. Furthermore, it is apparent that it enables the diaphragm to be removed as a unit with the coil, without necessitating the removal of any of the fastening members which hold the field coil and housing assembly together. Accordingly, it is not necessary to disturb the alignment between the inner and outer pole pieces in order to replace the diaphragm.

I claim: 7

1. In an electro-dynamic device, the combination of a field coil assembly including a coil, a shell, a front plate and a core, the core and front plate coacting to provide an air gap therebetween, means for clamping the plate with reference to the core, a diaphragm assembly including a diaphragm, a moving coil, and a spider, and means for clamping the spider to the field coil assembly independently of the first mentioned 4. An electro-dynamic device, comprising in combination, a field coil, a shell therefor, the shell having 'flanges at the open end thereof, a front plate bearing against the flanges and comprising an outer pole piece, a core carried by the shell and projecting through the front plate and comprising an inner pole piece, a diaphragm housing bearing against the front plate, common means for locking the housing, front plate and shell together, a diaphragm assembly including a frustro conical member, a moving coil and form therefor, and a spider, the spider embracing the diaphragm and form, and operating to lock them together as a unit, spaced arms engaging the housing and extending over the spider, and

threaded members for locking the clamping mem: bers and spider to the housing, said threaded members operating to permit removal of the diaphragm assembly without disturbing the connections between the field coil shell and housing.

5. In an electro-dynamic device, the combination with a diaphragm, a moving coil and a spider, all mounted for assembly as a unit, of a support, the spider having spaced shoulders therein, and clamping members bearing against the spider and having tongues engaging the shoulders, and means for locking the clamping members to the spider and support.

6. In an electro-dynamic device, the combination with a diaphragm assembly including a diaphragm, a moving coil and a spider all interconnected for movement as a unit, a support, clamping members carried thereby, said members enabling the assembly to be inserted into the support, and then turned and positioned beneath the clamping members, and adjusted for axial alignment. and other means for locking the clamping members to the spider and support.

'7. In an electro-dynamic device, the combination of a moving coil, a diaphragm and a I flexible spider, all mounted for movement as a unit, a support, and means for frictionally clamping the spider to the support, said means including a member that extends across the outer edge of the spider, and engages the support whereby the spider is locked to the support without imparting torsional stresses to any part of the spider.

BERNARD A. ENGHOLM. 

